The present disclosure relates to semiconductor devices, and particularly to transistors having a doping profile controlled by carbon-doped semiconductor material portions, and methods of manufacturing the same.
A raised source region is a semiconductor region that is deposited on a semiconductor region of a field effect transistor and functions as a part of a source region of the field effect transistor. A raised drain region is a semiconductor region that is deposited on a semiconductor region of a field effect transistor and functions as a part of a drain region of the field effect transistor. A raised source/drain region can be formed on a pre-existing source/drain region by a selective deposition process, which deposits a semiconductor material only on semiconductor surfaces and does not deposit any semiconductor material on a dielectric surface.
In some field effect transistors, the doping profile near the channel region can be controlled by diffusion of dopants from raised source and drain regions. A doping profile refers to the three-dimensional distribution of p-type dopants and n-type dopants in the channel and in the vicinity of the channel that includes at least the two p-n junctions between the body of the field effect transistor and each of the source region (including the raised source region) and the drain region (including the raised drain region) of the field effect transistor.
The doping profile affects various parameters of the field effect transistors, including, but not limited to, the on-current, the off-current, the threshold voltage, and the sub-threshold voltage slope. Modification of the doping profile can improve performance of field effect transistors by improving some performance parameters with, or without, a trade-off (degradation of some other performance parameters). However, in integration schemes that employ thermal dopant diffusion from raised source and drain regions as the mechanism for introducing dopants into source and drain regions, the dopant profile is a function of the geometry and diffusion parameters.